# Software

## SAS-DIF3DK (Reactor Dynamics and Safety Analysis Codes)

### Standard Code Description

**Name of Program:**

SAS-DIF3DK**Computer for Which Program is Designed and Other Machine Version Packages Available:**

Mainframe (IBM, CRAY, CDC, etc.), UNIX Workstation (SUN, IBM RISC, HP, SG), or Personal Computer (IBM PC) with FORTRAN Compiler.**Description of Problem Solved:**

SAS-DIF3DK is designed to perform deterministic analysis of coupled neutronics/thermal-hydraulic transients in water-cooled thermal reactors. Detailed, mechanistic models of steady-state and transient thermal, hydraulic, and neutronic phenomena are employed to describe the response of the reactor core to upsets caused by loss of coolant flow, loss of heat rejection, or control rod motions. The space-time neutronics capabilities of the DIF3D-K computer code are linked to a detailed reactor core thermal hydraulics model, which consists of transient fuel-cladding-coolant heat transfer calculations integrated with a single and two-phase water/steam fluid dynamics calculation. A flexible cross section specification capability based on the MACOEF format provides for transient adjustment of DIF3D-K group cross sections to reflect neutronic feedback due to fuel, coolant, and moderator temperature and density changes. Transient reactor power distributions calculated with DIF3D-K are used to drive the SAS channel thermal hydraulics simulation.**Method of Solution:**

In space, each SAS thermal-hydraulic channel represents one or more subassemblies with either a single pin model or a multiple pin model. Many channels are employed for a whole-core representation. Heat transfer in each pin is modeled with a two-dimensional (r/z) heat conduction equation. Single and two-phase coolant thermal-hydraulics are simulated with a one-dimensional (axial) nonequilibrium, homogenous coolant flow model. The DIF3D-K three- dimensional nodal spatial kinetics capability is employed, which permits either hexagonal-z or x-y-z Cartesian geometry. The SAS channel thermal-hydraulics are solved with an non-iterative implicit technique, and the coupling with the implicit DIF3D-K spatial kinetics solution is explicit at the time domain level.**Restrictions on the Complexity of the Problems:**

Dynamic data storage and retrieval techniques are employed to eliminate restrictions. Problem dimensions are limited only by available computer memory size.**Typical Running Time:**

Running times depend on the complexity of the model and the nature of the physical transient. A few-channel reactor model using only pin heat transfer, single phase coolant dynamics, reactor coolant loops, and reactor point kinetics physical models will generally run orders of magnitude faster than real time on modern computing platforms. A many-channel model with coolant boiling and spatial kinetics will take significantly longer, with running times that depend on problem complexity.**Unusual Features of the Program:**

The spatial kinetics and thermal-hydraulics models in SAS-DIF3DK are being developed with sufficient modeling flexibility to permit simulation of coupled transients in domestic U.S. and foreign water cooled reactors, including pressure tube designs moderated by graphite or heavy water.**Related and Auxiliary Programs:**

The DIF3D-K computer code is fully integrated into the SAS-DIF3DK program, which retains all the spatial kinetics capabilities of DIF3D-K.**Status:**

SAS-DIF3DK is being developed and validated at Argonne National Laboratory in the Nuclear Engineering Division.**References:**- H. S. Khalil, et al., "Coupled Reactor Physics and Thermal-Hydraulics Computations with the SAS-DIF3DK Code," Proceedings of the Joint International Conference on Mathematical Methods and Supercomputing for Nuclear Applications, Saratoga Springs, New York, October 59, Vol. 2, pp. 1063-1071, American Nuclear Society (1997).
- R. B. Turski, et al., "Macroscopic Cross section Generation and Application for Coupled Spatial Kinetics and Thermal Hydraulics Analysis with SAS-DIF3DK," Proceedings of the Joint International Conference on Mathematical Methods and Supercomputing for Nuclear Applications, Saratoga Springs, New York, October 59, Vol. 2, pp. 1072-1081, American Nuclear Society (1997).
- T. A. Taiwo, et al., "SAS-DIF3DK Spatial Kinetics Capability for Thermal Reactor Systems," Proceedings of the Joint International Conference on Mathematical Methods and Super-computing for Nuclear Applications, Saratoga Springs, New York, October 59, Vol. 2, pp. 1082-1096, American Nuclear Society (1997).
- F. E. Dunn, et al., "Computationally Efficient Thermal Hydraulics Calculations in the SAS-DIF3DK Coupled Reactor Physics and Thermal Hydraulics Code," Proceedings of the Joint International Conference on Mathematical Methods and Supercomputing for Nuclear Applications, Saratoga Springs, New York, October 59, Vol. 2, pp. 1097-1106, American Nuclear Society (1997).

**Machine Requirements:**

Memory requirements depend on problem specifications. Disk storage for potentially large ASCII print and binary plotting data storage files is required.**Programming Languages Used:**

FORTRAN 77 is used. System dependent routines may be supplied for dynamic memory allocation, timing, and system and user identification.**Operating System:**

No special requirements other than a FORTRAN compiler and the usual linker/loader facilities.**Other Programming or Operating Information or Restrictions:**

The SAS-DIF3DK computer code and any related documentation are subject to U.S. DOE Applied Technology regulations.**Name and Establishment of Author(s) or Contributor(s):****J. E. Cahalan**

Nuclear Engineering Division

Argonne National Laboratory

9700 South Cass Avenue

Argonne, Illinois 60439

**Materials Available:**

Because of its developmental nature, SAS-DIF3DK is not being distributed.**Sponsor:**

U.S. Department of Energy, Office of Nuclear Energy, Science, and Technology.

Last Modified: Wed, April 20, 2016 9:51 AM